Python-style generators in Go

Question

I\'m currently working through the Tour of Go, and I thought that goroutines have been used similarly to Python generators, particularly with Question 66. I thought 66 looked co

Answer 1

Yes, increasing the buffer size might drastically increase the execution speed of your program, because it will reduce the number of context switches. Goroutines aren't garbage-collected, but channels are. In your example, the fibonacci goroutine will run forever (waiting for another goroutine to read from the channel c), and the channel c will never be destroyed, because the fib-goroutine is still using it.

Here is another, sightly different program, which do not lack memory and is imho more similar to Python's generators:

package main

import "fmt"

func fib(n int) chan int {
    c := make(chan int)
    go func() {
        x, y := 0, 1
        for i := 0; i <= n; i++ {
            c <- x
            x, y = y, x+y
        }
        close(c)
    }()
    return c
}

func main() {
    for i := range fib(10) {
        fmt.Println(i)
    }
}

Alternatively, if you do not know how many Fibonacci numbers you want to generate, you have to use another quit channel so that you can send the generator goroutine a signal when it should stop. This is whats explained in golang's tutorial https://tour.golang.org/concurrency/4.